ABSTRACT
FIGURE 1-1 Cost of ownership as a function o f re liability and main tainability
TABLE 1-1 Hierarchical levels for digital computers
Level/Sublevel Components Level/Sublevel Components
PMS (highest level) Processors Logic Memories Switching circuit Sequential Switches Flip-flops; latches; delays Controllers Combinatorial Transducers Gates; encoders/decoders; Data operators data operators Links Register transfer Data
Program Registers; operators; data paths ISP Memory state
Processor state Effective address
calculation Instruction decode Instruction execution
Circuit (lowest level)
Control Hardwired
Sequential logic machines Microprogramming
Microsequencer; microstore
Resistors High-level language Software Capacitors
Inductors Power sources Diodes Transistors
TABLE 1-2 Stages in the life of a system
Stage Error Sources Error Detection Techniques
Specification and design Algorithm design Formal specifications
Simulation Consistency checks
Prototype Algorithm design Wiring and assembly Timing Component failure
Stimulus/response testing
Manufacture Wiring and assembly Component failure
System testing Diagnostics
Installation Assembly Component failure
System testing Diagnostics
Operational life Component failure Operator errors Environmental fluctuations
Diagnostics
TABLE 1-3 Probability of operational outage caused by various sources
Source of Outage
AT&T Switching Systems
[Toy, 1978]a Bellcore
[Ali, 1986]a
Japanese Commercial
Users Tandem
[Gray, 1985] Tandem
[Gray, 1987] Northern Telecom
Mainframe Users
Hardware 0.20 0.26e 0.75f 0.18 0.19 0.19 0.45 Software 0.15 0.30d 0.75' 0.26 0.43 0.19 0.20 Maintenance — --- 0.75f 0.25 0.13 — 0.05 Operations 0.65b 0.44e 0.11 0.17 0.13 0.33 0.15 Environment
— — 0.13 0.14 0.12 0.28s 0.15
FIGURE 1-2 Reliability demon stration chart for monitoring the progress o f a de sign maturity test [From data in von Alven, 1964]
The Manufacturing Stage
FIGURE 1-3 Typical steps in the manufacture o f a digital system, [From Foley, 1979; © 1979 IEEE]
FIGURE 1-4 Bathtub-shaped curve depicting component failure rate as a function of time
FIGURE 1-5 Factors that con tribute to the fail ure rate o f a com ponent over time
Approximately 5 to 25 20 weeks years
Time
Time
FIGURE 1-6 Potential annual savings from screening and test ing as a function of annual compo nent volumes [From Craig, 1980]
1 10 100 1,000 10,000
Yearly component volume in thousands
The Operational Life Stage
FIGURE 1-7 Failure rate per gate as a function of chip complexity for bipolar tech nology
rocf“
r a 2Atl2
FIGURE 1 -8 Improvement in hard failure rate for IBM mainframes
Year of introduction
Passes on failure data
FIGURE 1 -9 DEC'S Remote Diagnosis Network
Customer Satisfaction
The Designable Parameters
Designable Parameter Measure of Customer Satisfaction
Increased mean time to failure Decrease number of times computer is unavailable for operation
Decreased mean time to repair Decrease amount of time computer is unavailable when a failure occurs
Increased mean time to crash Decrease the probability that data is lost
FIGURE 1-10 Major activities in the design and marketing o f a computer system
